Oxymcrcuration of (R)-sulcatol (1) to (3R,6R)-2 was followed by its treatment with NaBH, and oxygen lo give (3S,6R)-tetra-Iiydro-2,2,6-trimethyl-2H-pyran-3-01 ( 3 4 and (3R,6R)-3n'. In thc same manner, (3R.69-3a and (3S,GS)-3a' were synthesized from ( Q I .
Tetrahydro-2,2,6-trimethyl-2H-pyran-3-01 (3) was recently isolated by Francke and Klimetzek as a volatile compound from the elm bark beetle Pteleobius vittatus2). In order to clarify the stereochemistry of that natural product, it was necessary to synthesize all of its stereoisomers, (3S,6R)-3a, (3R,6S)-3a, (3R,6R)-3a', and (3S,6S)-3a'. This note describes the conversion of sulcatol enantiomers [(R)-and (S)-l] into the four stereoisomers of the tetrahydropyran.
The pure enantiomers of sulcatol (1) were prepared as reported previously3). Oxymer~uration~) of (R)-1 with mercuric acetate was followed by the addition of brine to give in 83% yield the crystalline (tetrahydropyrany1)mercuric chloride (3R,6R)-2 ' -' ) with the axial protons at C-3 (6 = 2.73, dd; J = 6, 12 Hz) and at C-6 (6 = 3.76, ddq; J = 2.5, 11.5, 6 Hz). Treatment of (3R,6R)-2 with NaBH4 in N,N-dimethylformamide saturated with molecular oxygen furnished a mixture of two alcohols in a ratio of 1.0: 1.1. These were ,,." (R) -1 (3R,6R)-2 , , 4 QoR ,#' .A" + *." aoR ..+' (3R,6R)-3a': R-H (35.6R)-3 a: R=H b R=(R)-MTPA b': R=(R)-MTPA (35.6s) -2
(5) -1 (3R,65) -3